How to Understand Kinetic Versus Thermodynamic

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This article is originally started by somebody else. I found it interesting to correct it. But it needs a full attention that I might commit later. For now!


  1. Note that Chemical reactions are governed like any other system in the world by the rule that says that any system at a specified state will take the path with minimum energy to get to another specified state. This principle is basic to all objects and there is no exception to this rule even in processes maintaining and sustaining the life, when all thermodynamics parameters are carefully defined.
    • Living systems have chemical reactions within their bodies, known as biochemical reactions, that requires intake of energy counted (with the abuse of the words) in the form of calories.
  2. Apply this principle of thermodynamic stability and minimum energy state to chemical systems. Certain reactions reach in a state of equilibrium between compounds participating in the reaction and the products which are expected as the outcome of the reaction. To clarify, for instance, only ten per cent of the intake materials will give the desired product. It is due to the fact that in the given thermodynamic condition the product disassociate back to the input compounds. In such conditions either the product should be removed as fast as possible before disintegration to disturb the balance (concentration) of materials in favour of more productive reaction or new thermodynamic conditions should be imposed to overcome the kinetic (dp/dt) of the reaction towards production rather than decomposition. The parameters include change of pressure and temperature or the volume of the reaction.
  3. Become familiar with kinetics factors. Another concept comes into play here which is called kinetics. One concept from this theory is the activation energy of a chemical reaction. That is, having two stable states with one in lower energy there might be a barrier between them that should be overcome by the reaction to move from the higher state to the lower state. As an example hydrogen molecules and nitrogen molecules can exist stable next to each other, but to react and form ammonia they need to overcome a barrier. A lightening in the sky helps to create heat and overcomes the barrier and creates H3N. Raining immediately converts it to NH4OH washes it down to earth decreases the concentration of H3N in the atmosphere and helps more nitrogen and hydrogen reaction in the next lightening. At the same time, the same phenomenon happens to nitrogen and oxygen to create nitric acids to be neutralised by ammonia and, meanwhile, land becomes fertilised by natural ammonia nitrate products.
    Overcoming the Kinetic Barrier
    A reaction can be thermodynamically favourable and yet does not proceed. This is basically due to a kinetic factor which is manifested by a high energy barrier for this specific reaction. Therefore, a reaction which is thermodynamically favourable can be kinetically disfavoured due to the presence of high energy barrier. A thermodynamic product of a given chemical reaction is always the more selective and energetically favoured compound. The energy profile for such a reaction is downhill. Also, thermodynamic products are usually obtained in the process which is slower and more selective due to its being energetically driven. To sum up, factors affecting a reaction are
    • Pressure, temperature, concentration/volume, and catalysts.
    • The other type of products which are also observed in some chemical reaction is called the kinetic product. This type of product in a certain chemical reaction is usually less stable thermodynamically and possesses excessive energy which makes it unstable species that tend to decompose instantly with the help of any perturbation such as shock or heat. Also, unstable compounds that are considered in a state of kinetic stability include ether solvents that underwent a process of peroxide formation.
  4. Learn about delay boiling and delay solidification. Put a bottle of beer standing in a freezer for an hour. Then gently bring it out. Put it on a table and smoothly open its cap. Beer is in liquid phase. Tap it with the tip of your nail or drop a grain of salt in it. Suddenly all the bottle turns into a slush. Though the bottle in terms of thermodynamic variables was in freezing condition it needed a kinetic spur such as a turbulence or seed for crystallisation to militaristically (martensitic type) transforms to new solid phase. (Be careful not to leave the bottle too long in freezer otherwise it blows.)
  5. Become familiar with the concept of chemical potential. It is a coefficient of number of particles involved in the chemical reaction that modifies thermodynamic equation of energy in a way that energy of each mole of particles to be taken into the account.